Corleone family consigliere Tom Hagen Robert Duvall is his informally adopted brother. The character of Fredo is more indecisive and lacks the determination of his brothers, and as a result has little power or status within the Corleone crime family.
In the novel, Fredo's primary weakness is his womanizing , a habit he develops after moving to Las Vegas and which earns his father's disfavor. In the films, Fredo's feelings of personal inadequacy and his inability to act effectively on his own behalf are character flaws leading to his demise. In a pivotal scene in the novel and film, Fredo is with his father when assassins working for drug kingpin Virgil Sollozzo Al Lettieri gun down Don Corleone in the street.
Fredo, terrified, fumbles and drops his gun, failing to return fire. He sits on the curb next to his severely wounded father, weeping. In the novel, Fredo is sickened after witnessing his father being shot, going into shock. To aid Fredo's recovery and protect him from possible reprisals, Sonny sends his younger brother to Las Vegas under the protection of Don Anthony Molinari of San Francisco. While in Las Vegas, Fredo learns the casino trade and becomes acquainted with former hitman Moe Greene Alex Rocco , who runs a major Vegas hotel that the Corleone family bankrolled.
This angers Greene, who ends up slapping Fredo in public on at least one occasion. This creates a lasting rift between the two surviving brothers.
When Michael learns that Greene slapped Fredo, he is angered and confronts Greene, but is also dismayed when Fredo comes to Greene's defense. When Fredo berates Michael for being hostile to Greene, Michael in turn threatens Fredo for taking sides against their family during a meeting with Greene, warning him never to do so again.
